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Uniformitarianism
Assumption that natural laws are constant through time and space
Assumption that natural laws are constant through time and space
Uniformitarianism, also known as the Doctrine of Uniformity or the Uniformitarian Principle, is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe. It refers to invariance in the metaphysical principles underpinning science, such as the constancy of cause and effect throughout space-time, but has also been used to describe spatiotemporal invariance of physical laws. Though an unprovable postulate that cannot be verified using the scientific method, some consider that uniformitarianism should be a required first principle in scientific research.
In geology, uniformitarianism has included the gradualistic concept that "the present is the key to the past" and that geological events occur at the same rate now as they have always done, though many modern geologists no longer hold to a strict gradualism. Coined by William Whewell, uniformitarianism was originally proposed in contrast to catastrophism by British naturalists in the late 18th century, starting with the work of the geologist James Hutton in his many books including Theory of the Earth. Hutton's work was later refined by scientist John Playfair and popularised by geologist Charles Lyell's Principles of Geology in 1830. Today, Earth's history is considered to have been a slow, gradual process, punctuated by occasional natural catastrophic events.
History
18th century
Abraham Gottlob Werner (1749–1817) proposed Neptunism, where strata represented deposits from shrinking seas precipitated onto primordial rocks such as granite. In 1785 James Hutton proposed an opposing, self-maintaining infinite cycle based on natural history and not on the Biblical account.
:1st, That the land on which we rest is not simple and original, but that it is a composition, and had been formed by the operation of second causes.
:2nd, That before the present land was made, there had subsisted a world composed of sea and land, in which were tides and currents, with such operations at the bottom of the sea as now take place. And,
:Lastly, That while the present land was forming at the bottom of the ocean, the former land maintained plants and animals; at least the sea was then inhabited by animals, in a similar manner as it is at present.
Hence we are led to conclude, that the greater part of our land, if not the whole had been produced by operations natural to this globe; but that in order to make this land a permanent body, resisting the operations of the waters, two things had been required;
:1st, The consolidation of masses formed by collections of loose or incoherent materials;
:2ndly, The elevation of those consolidated masses from the bottom of the sea, the place where they were collected, to the stations in which they now remain above the level of the ocean.}}
Hutton then sought evidence to support his idea that there must have been repeated cycles, each involving deposition on the seabed, uplift with tilting and erosion, and then moving undersea again for further layers to be deposited. At Glen Tilt in the Cairngorm mountains he found granite penetrating metamorphic schists, in a way which indicated to him that the presumed primordial rock had been molten after the strata had formed. He had read about angular unconformities as interpreted by Neptunists, and found an unconformity at Jedburgh where layers of greywacke in the lower layers of the cliff face have been tilted almost vertically before being eroded to form a level plane, under horizontal layers of Old Red Sandstone. In the spring of 1788 he took a boat trip along the Berwickshire coast with John Playfair and the geologist Sir James Hall, and found a dramatic unconformity showing the same sequence at Siccar Point. Playfair later recalled that "the mind seemed to grow giddy by looking so far into the abyss of time", and Hutton concluded a 1788 paper he presented at the Royal Society of Edinburgh, later rewritten as a book, with the phrase "we find no vestige of a beginning, no prospect of an end".
Both Playfair and Hall wrote their own books on the theory, and for decades robust debate continued between Hutton's supporters and the Neptunists. Georges Cuvier's paleontological work in the 1790s, which established the reality of extinction, explained this by local catastrophes, after which other fixed species repopulated the affected areas. In Britain, geologists adapted this idea into "diluvial theory" which proposed repeated worldwide annihilation and creation of new fixed species adapted to a changed environment, initially identifying the most recent catastrophe as the biblical flood.
19th century
From 1830 to 1833 Charles Lyell's multi-volume Principles of Geology was published. The work's subtitle was "An attempt to explain the former changes of the Earth's surface by reference to causes now in operation". He drew his explanations from field studies conducted directly before he went to work on the founding geology text, and developed Hutton's idea that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time. The terms uniformitarianism for this idea, and catastrophism for the opposing viewpoint, was coined by William Whewell in a review of Lyell's book. Principles of Geology was the most influential geological work in the middle of the 19th century.
Systems of inorganic earth history
Geoscientists support diverse systems of Earth history, the nature of which rests on a certain mixture of views about the process, control, rate, and state which are preferred. Because geologists and geomorphologists tend to adopt opposite views over process, rate, and state in the inorganic world, there are eight different systems of beliefs in the development of the terrestrial sphere. All geoscientists stand by the principle of uniformity of law. Most, but not all, are directed by the principle of simplicity. All make definite assertions about the quality of rate and state in the inorganic realm.
Methodological
assumption concerning
kind of process
Substantive claim
concerning state
Substantive claim
Concerning rate
System of Inorganic
Earth history
Promoters
Same Kind of processes
that exist today
Actualism
Steady State
Non-directionalism
Constant Rate
Gradualism
Actualistic
Non-directional
Gradualism
Most of Hutton, Playfair, Lyell
Changing Rate
Catastrophism
Actualistic
Non-directional
Catastrophism
Hall
Changing State
Directionalism
Constant Rate
Gradualism
Actualistic
Directional
Gradualism
Small part of Hutton, Cotta, Darwin
Changing Rate
Catastrophism
Actualistic
Directional
Catastrophism
Hooke, Steno, Lehmann, Pallas,
de Saussure, Werner, and geognosists,
Elis de Beaumont and followers
Different Kind of processes
than exist today
Non-Actualism
Steady State
Non-directionalism
Constant Rate
Gradualism
Non-Actualistic
Non-directional
Gradualism
Carpenter
Changing Rate
Catastrophism
Non-Actualistic
Non-directional
Catastrophism
Bonnet, Cuvier
Changing State
Directionalism
Constant Rate
Gradualism
Non-Actualistic
directional
Gradualism
De Mallet, Buffon
Changing Rate
Catastrophism
Non-Actualistic
Directional
Catastrophism
Restoration cosmogonists,
English diluvialists,
Scriptural geologists
Lyell
Lyell's uniformitarianism is a family of four related propositions, not a single idea:
Uniformity of law – the laws of nature are constant across time and space.
Uniformity of methodology – the appropriate hypotheses for explaining the geological past are those with analogy today.
Uniformity of kind – past and present causes are all of the same kind, have the same energy, and produce the same effects.
Uniformity of degree – geological circumstances have remained the same over time.
None of these connotations requires another, and they are not all equally inferred by uniformitarians.
Gould explained Lyell's propositions in Time's Arrow, Time's Cycle (1987), stating that Lyell conflated two different types of propositions: a pair of methodological assumptions with a pair of substantive hypotheses. The four together make up Lyell's uniformitarianism.
Methodological assumptions
The two methodological assumptions below are accepted to be true by the majority of scientists and geologists. Gould claims that these philosophical propositions must be assumed before you can proceed as a scientist doing science. "You cannot go to a rocky outcrop and observe either the constancy of nature's laws or the working of unknown processes. It works the other way around." You first assume these propositions and "then you go to the outcrop."
:* Uniformity of law across time and space: Natural laws are constant across space and time.
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